The light source of liquid crystal display (LCD) screens that are now being commonly used on desktop and notebook computers, PDAs, and Webpads is generated by a cold cathode fluorescent lamp (CCFL) actuated by a driving unit under a high voltage that projects light to a back panel so that displaying pictures become visible to users.
The LCD TV or LCD screen with a membrane touch screen requires a greater illumination to compensate visual requirements. The general driving device for actuating the CCFL as shown in FIG. 1 usually uses one PWM control unit to drive one driving unit, then the driving unit drives the transformer and load (CCFL). The CCFL is ignited by a high voltage. A greater current will generate a greater illumination.
When the illumination and evenness of the back light is not sufficient, a plurality of lamps are needed. To meet this requirement, the number of the PWM control unit for driving the ignition, driving unit, and transformer also increases. As a result, the size of the circuit board becomes larger, and manufacturing is more difficult and the cost increases.